Key Points

  • Urinary stones affect about 10% of people in Japan and can cause sudden, severe pain and infection.
  • The most common types are calcium oxalate and uric acid stones, with risk increased by diet, dehydration, obesity, and some medications.
  • Prevention focuses on adequate hydration (aim for a urine volume of 1.5 to 2 liters or more per day), maintaining appropriate dietary calcium, reducing salt and excessive animal protein, and adjusting cooking methods for high-oxalate foods.
  • Extreme diets, such as the ketogenic diet, can increase the risk of stone formation and should be approached with caution.

What Are Urinary Stones? — A Common Cause of "Sudden, Severe Pain"

Urinary stones are a condition where stones formed in the kidneys drop into the ureter, causing severe pain, blood in the urine, and infection. According to Jikei University School of Medicine, the lifetime prevalence among Japanese people is about 10%, making it a disease we often hear people around us say they have "experienced once." In the early stages, there may be no symptoms, and they might be found accidentally during a health checkup. However, when a stone moves, it is characterized by an unbearable pain that shoots from the flank to the lower abdomen. The NHS (National Health Service in the UK) and domestic university hospitals also state that early diagnosis and lifestyle improvements are key to preventing recurrence.

Types and Causes of Stones

Main Types and Mechanisms

The most typical ones are calcium oxalate stones and uric acid stones. Calcium oxalate stones are formed when oxalate absorbed from the intestines binds with calcium. Uric acid stones are more likely to form when uric acid levels in the blood are high, and they are associated with gout. Dehydration, excessive salt intake, excessive animal protein, obesity, and intestinal malabsorption (such as from intestinal surgery or inflammatory bowel disease) also increase the risk.

The Impact of Food

Foods high in oxalate include spinach, beetroot, nuts, chocolate, and black tea. In addition to avoiding these, you can reduce the amount of oxalate in foods by boiling them and discarding the cooking water. On the other hand, extremely reducing dietary calcium can paradoxically increase the risk of stones, so it is important to maintain an appropriate intake of calcium from your diet. Citric acid (found in lemons and limes) works to suppress the growth of crystals in the urine, and our team has also felt the benefits since making morning lemon water a habit.

Prevention and Daily Measures

Ensuring Hydration and Urine Volume

The most effective measure is adequate fluid intake. It is said to be good to aim for a urine volume of 1.5 to 2 liters or more (for adults). Drink frequently before you feel thirsty, and be consciously sure to hydrate, especially during exercise or in the summer.

Dietary Points

・Reduce salt intake (excessive salt increases calcium excretion in the urine).
・Avoid excessive intake of animal protein (it promotes uric acid levels and acidification of the urinary tract).
・Get an appropriate amount of calcium from your diet (dairy products are a safe choice).
・Be careful with high-dose vitamin C supplements, as taking large amounts over a long period can potentially turn into oxalate in the body.
・Incorporate citric acid by consuming citrus fruits (such as lemon water).

Lifestyle and Medical Responses

Obesity management and a regular diet help lower the risk of stones. For those with a history of stones or frequent recurrences, a 24-hour urine test can be used to check for risk factors, and doctors may prescribe thiazide diuretics or citrates as needed. We also have family members with a history of stones, and we have experienced that recurrenc